Seismic Velocities Contain Information about Depth, Lithology, Fluid Content, and Microstructure

Berge, Patricia A.; Bonner, B.P.

doi:10.4133/1.2927173

Cited by 8 publications

(4 citation statements)

References 9 publications

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“…Such factors usually affect Vp and Vs in different ways. Typically, the spatial variation of Vp mirrors the distribution of lithologies and rock properties, while the Vp/Vs ratio maps rock defects, pores, cracks, and their fluid content [Berge and Bonner , 2002]. Since Vp and Vp/Vs are affected by different phenomena, both distributions have to be combined to envisage a global seismic structure.…”

Section: Discussionmentioning

confidence: 99%

Seismic tomography of Central São Miguel, Azores

Zandomeneghi

Almendros

Ibáñez

et al. 2008

Physics of the Earth and Planetary Interiors

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Section: Discussionmentioning

confidence: 99%

Seismic tomography of Central São Miguel, Azores

Zandomeneghi

Almendros

Ibáñez

et al. 2008

Physics of the Earth and Planetary Interiors

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“…Recent studies showed that mesoscopic patches are created during drainage process implying strong differences of velocity (Cadoret et al 1995; Monsen & Johnstad 2005; Lebedev et al 2009) contrary to imbibition where the saturation is more homogeneous. Other studies (Domenico 1977; Berge & Bonner 2002) in unconsolidated media showed that the effective fluid model remains valid in this high frequency range even if some discrepancies can be attributed to microscopic patchy saturation at high pressure and water saturation. At lower frequencies (20 kHz), George et al (2009) showed that the seismic velocity and attenuation strongly depend on the fluid saturation history in compacted heterogeneous soils similarly to some observation in rocks (Cadoret et al 1995, 1998).…”

Section: Introductionmentioning

confidence: 86%

Laboratory monitoring of <italic>P</italic> waves in partially saturated sand

2012

Geophysical Journal International

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SUMMARY Energy dissipation is observed on seismic data when a wave propagates through a porous medium, involving different frequency regimes depending on the nature of rock and fluid types. We focus here on the role of partial fluid saturation in unconsolidated porous media, looking in particular at P‐wave phase velocity and attenuation. The study consists in running an experiment in a sand‐filled tank partially saturated with water. Seismic propagation in the tank is generated in the kHz range by hitting a steel ball on a granite plate. Seismic data are recorded by buried accelerometers and injecting or extracting water controls the partial saturation. Several imbibition/drainage cycles were performed between the water and gas residual saturations. A Continuous Wavelet Transform applied on seismic records allowed us to extract the direct P wave at each receiver. We observe an hysteresis in phase velocities and inverse quality factors between imbibition and drainage. Phase velocities and inverse quality factors are then jointly inverted to get a final poro‐viscoelastic model of the partially saturated sand that satisfactorily reproduces the data. The model formulation consists in generalizing the Biot theory to effective properties of the fluid and medium (permeability and bulk modulus) to properly explain the phase velocity variation as a function of the saturation. The strong level of attenuation measured experimentally is further explained by an anelastic effect due to grain to grain sliding, adding to Biot’s losses. This study shows that fluid distribution at microscopic scale has strong influence on the attenuation of direct P waves at macroscopic scale and confirms that seismic prospection may be a powerful tool for the characterization of transport phenomena in porous media.

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“…However, Naesgaard et al (2007) found that p-wave velocity was high in laboratory test specimens known to be unsaturated based on measurement of low B-values, and postulated that the p-wave may propagate around air bubbles through fully-saturated channels in the soil. Berge and Bonner (2002) provide further discussion of the influence of pore fluid heterogeneity, and suggest methods for distinguishing uniform versus "patchy" saturation based on p-wave and s-wave velocity measurements. Heterogeneity in the distribution of air bubbles in the void space and differential inertial effects would be expected to result in higher V p values than predicted by Eq.…”

Section: Influence Of Impedance Mismatch Between Soil and Transducermentioning

confidence: 99%

CPT‐Based Ultrasonic Probe for P‐Wave Reflection Imaging of Embedded Objects

Coe¹,

Brandenberg²

2011

Symposium on the Application of Geophysics to Engineering and Environmental Problems 2011

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An ultrasonic p-wave reflection imaging probe is developed and utilized to noninvasively image the geometry of a deep foundation supporting a bridge pier. The source ultrasonic transducer emits compressive waves into saturated soil that subsequently transmit to and reflect back from an embedded object, and the receiver transducer measures the reflections which are used to construct an image. The components of the system, including the custom transducer probe and data acquisition hardware, were integrated with the nees@UCLA cone penetration testing (CPT) truck. The transducers have a central frequency of 100kHz, and have a diameter-to-wavelength ratio of more than 3 in soft saturated soils with p-wave velocities similar to water (i.e., 1500m/s). The large diameter-to-wavelength ratio gives the transducers a directivity pattern that controls the rate at which wave amplitude attenuates with distance. The transducers are impedance matched to water, and are therefore reasonably efficient transmitters in saturated soil, but inefficient in unsaturated soil. The probe was utilized to successfully image a pile foundation in very soft saturated clay, but returns were not recorded in stiffer and/or unsaturated soils. Causes of the poor returns include the scattering effects of large soil particles, coupling between the transducers and the soil, and drift of the probe out of alignment with the pile foundation. The probe could be very useful for nondestructive quality assurance of structural elements constructed in-situ in soft saturated soils,

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Seismic Velocities Contain Information about Depth, Lithology, Fluid Content, and Microstructure

Abstract: This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the author.

Cited by 8 publications

References 9 publications

Seismic tomography of Central São Miguel, Azores

Seismic tomography of Central São Miguel, Azores

Laboratory monitoring of <italic>P</italic> waves in partially saturated sand

CPT‐Based Ultrasonic Probe for P‐Wave Reflection Imaging of Embedded Objects

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